There's a campaign for an "In or Out?" referendum in the UK. Some think it's a good idea, others think it's a bad idea. It's a question that will need to be asked in the UK at some point, since it's hard to have a clear policy on how to act in the EU if the UK government outwardly agrees with - or at least plays along with - the eurosceptic press, but deals with the reality of EU membership when it comes to business. As Eurogoblin has explained, it's not a very high priority issue for the British public, which makes the opinion polls on the matter interesting: if people don't really care, does that mean that their opinion is "soft" and may change or harden depending on a referendum campaign? It has the potential to make a referendum campaign very interesting. Eurogoblin, in an article on Tony Blair's book, has also touched on another interesting point: the difficulty a eurosceptic party - or one that makes eurosceptic noises - has in winning power in the UK. Or, to put it another way, the difficulties such parties have in appearing mainstream and acceptable.
It's unlikely that it will get anywhere soon. Hannan is far from the mainstream in the UK, and even he seems to present it as a long-term campaign to change the attitudes for government so it will eventually happen.
Still, if it ever happens, and there's a "Yes" vote, what about holding referendums on the opt-outs? To see how far "In" people want to be, if they want to be in the EU at all.